Local people have accidentally unearthed nearly 100 age-old cannon balls recently at a site located 3km away from the world-heritage Ho Dynasty Citadel, Vinh Loc district, central Thanh Hoa province.

Buried around 50–70 centimeters beneath the ground, the round shot, which were carefully polished, have diameters ranging from 5-8 centimeters. Most of them were made from limestone, while the rest were from pebble and sandstone.

Ammunition similar to these in terms of materials, shapes, sizes and technique was once excavated at the Ho Dynasty Citadel. A theory believes that all of them, as popular military equipment during the reign of Ho Quy Ly (1398-1407), were used for cannons invented by Ho Nguyen Trung, the King’s first son.